For these I always pick numbers every once in a while in doesnt work and algebra is necessary but it usually gets the job done. Let X =100m/sec therefore Y would be 100/1000km/sec than multiply by 60*60 sec per hour leaves you with Y=360km/hr. Plug 100 in to the answer choices to see which give you a Y =360 answer is B. Not sure if that is the fastest way to do it,but I can get that one done in about 45 seconds which I think is a very good time to give you a little extra on some of the ones you find more challenging. This test is so frustrating because you never know what they consider difficult versus what you consider difficult.

IMO - C.

Y Km/h = (Y*1000)/(60*60) m/s
= (18/5)x

You're right the answer is c. 18x/5.
but i can't figure out how you got it though. Can you explain maybe with the numbers? I'm plug in numbers in Y Km/h = (Y*1000)/(60*60) m/s
but i don't come up with same thing

If the speed of x meters per second is equivalent to the speed of y kilometers per hour, what it y in terms of x ( 1 kilometer = 1000 meters)

a) 5x/18
b) 6x/5
c) 18x/5
d) 60x
e) 3,600,000x

C is right that was my mistake in transposing the answers sorry about that. 1800/5=360 so C 18x/5

janvierek, here is how I figured it out.

I wrote the equation x meters/sec = y kms/hour

Now I have to solve for y. To get y by itself, multiply both sides by the hour, just like you normally would any algebraic equation:

(x meters * 1 hour)/sec = y kms

Since I have an hour on top and seconds on the bottom, I converted the hour to seconds so they would cancel:

(x meters * 3600seconds)/sec = y kms and the seconds cancel leaving:

3600 * x meters = y kms Now to isolate the y, I need to divide by the kms, but convert it to meters so the meters will cancel:

3600xmeters/1000meters=y

36x/10=y

y=18x/5

I hope that makes sense. People on here are so good at math I often can't see the shortcuts they take.